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المستخلص Telomere dynamics are considered highly significant in the development of cancer cells. Increased expression or amplification of hTERT and hTERC genes was reported to induce upregulation of telomerase enzyme and telomere lengthening. Amplification of these genes are now believed to play important role in confirmation of diagnosis and prognosis of cancer cell line. Increased expression of these genes is attributed to alteration of their regulatory mechanisms. Both genes seems to be parallel in most of their regulatory mechanisms. Yet some cases, where both genes are not parallel to each other suggest other regulatory factors of hTERC that needs further studies. Concerning hematological malignancy, many studies revealed amplification or increased expression of the hTERT and hTERC genes, increased telomerase activity and telomere length maintenance in pediatric acute lymphoblatic leukemia. It was reported that these series of events are common events in leukemogenesis. In the light of this, the current study aimed to detection of hTERT and hTERC genes amplification in pediatric acute lymphoblatic leukemia by FISH analysis and its relation to standard prognostic factors and patient outcome. The study was carried out on 25 pediatric newly diagnosed ALL patients, attended Ain Shams university hospitals. Their ages ranged from 0.9 to 9 years old with a mean value of 4.78±2.1. They were 13 males and 12 females with male to female ratio of 1.1: 1. Summary 203 Detection of amplification of hTERT and hTERC by FISH technique using dual colour LSI probes (5 P 15.33 / 5 q 31) for hTERT gene and (3q26 / alphasatallite) for hTERC gene in pediatric patients with acute lymphoblastic leukemia at diagnosis and at first hematological remission. Follow up was done for 6-24 months following the diagnosis and induction therapy as regard first hematological remission after initial induction dose at day 28 to 35, complete remission or hematological, CNS or testicular relapse in males. hTERT and hTERC genes amplification was detected in all bone marrow samples by FISH analysis and revealed amplification in 100% and 92% of examined cases, at diagnosis respectively. At first hematological remission hTERT and hTERC genes revealed amplification in 72% and 64% of examined cases, respectively. Number of copies of hTERT and hTERC genes was also concerned in this study. At diagnosis, wide range of hTERT copy number, ranging from 2 to 22 copies per examined interphase cell was detected. hTERC gene copy number, on the other hand, ranged from 2 to 15 copies with relative decrease in copy number at first hematological remission. In contrast, normal subjects revealed 2 copies per interphase cell. Regarding relation to prognostic factors, hTERT revealed positive correlation to LDH at diagnosis and at first hematological remission while hTERC revealed positive correlation to LDH at diagnosis only. Besides, a positive correlation between blast percent at first hematological remission and hTERT and hTERC genes percentage of amplification. This was evident both at diagnosis and on day 28-38 of induction therapy. Summary 204 Also significant increase in percentages of amplification of hTERT and hTERC genes was evidenced in patient groups with extramedullary infiltration. By follow up of studied case, hTERT and hTERC genes percentages of amplification showed higher levels in patients with inferior outcome. So these genes play important role not only in confirmation of diagnosis but also in prognosis of studied cases. It was proved in this study that hTERT gene is the best gene in prediction of relapse as regard its percentage of amplification at first hematological remission; at day 28 to 35 of induction therapy. A cutoff value of 6.5% of amplification of hTERT gene was found to be reliable in prediction of relapse with sensitivity of 100%, specificity of 71%, PPV of 64%, NPV of 100% and diagnostic accuracy of 81%. At the level of copy number, cases with hTERT and hTERC genes copy number of 10 or more were found to be of bad prognosis. This was reported in many studies to be due to increased telomerase activity by 30 to 50%. Besides, patients with 10 or more copy number revealed shorter OS and RFS times. The current study findings go with the fact reported by many studies that telomerase genes amplification is a diagnostic and prognostic tool in pediatric ALL. |